In present coffee machines, the filter-carrying cups are introduced in a cylindrical recess surrounding the pressurizer provided with its water inlet sprinkling grill.
The securement of a filter-carrying cup in such a cylindrical recess is achieved by means of a bayonet connection combined with helicoidal ramps permitting obtaining simultaneously the progressive compression of the dose of ground coffee, previously introduced into the filter, before securement of the filter-carrying cup to the coffee machine, and the seal between the edge of the filter-carrying cup and the cup joints situated about the pressurizer, in the bottom of the recess. This is the case for the patents FR-A-666,825, BE-A-894,192, FR-A-574,079 and DE-B-1,077,843.
To do this, the filter-carrying cup comprises, at its periphery, two diametrically opposed projections adapted to engage in free spaces between two helicoidal ramps, located at the base of the interior of the cylindrical recess. It suffices, after having introduced a filter-carrying cup into said recess and having engaged its projections on the lower end of the ramps, to exert, on said filter-carrying cup, with the aid of the handle with which it is provided, a rotative couple in the direction and with sufficient force to obtain both the temporary securement of the filter-carrying cup to the cylindrical recess, the compression of the dose of coffee and sufficient penetration of the cup joint to ensure sealing.
Removal of the filter-carrying cup, after the infusion has flowed out into the cup or cups, takes place much more easily because it suffices to exert a shock in the opposite direction on the handle of the cup, to obtain loosening of the edge of the cup relative to the cup joint and the sliding, in the reverse direction, of the projections along the helicoidal ramps, toward complete disengagement.
Such devices, although they give together satisfaction from a strictly functional standpoint, nevertheless have certain major drawbacks, that should be emphasized.
First of all, the user must ensure precise positioning of the filter-carrying cup relative to the recess, to obtain the engagement of the projections on the end of the ramps, which are, by their nature, masked from view.
Then, a rather great effort must be exerted on the handle of the filter-carrying cup, to obtain the complete engagement of the filter carrier in its recess, this force must be sufficient to overcome the frictional resistances between projections and ramps; as a result, there is a certain cumulative fatigue suffered by persons who by their occupation must repeatedly daily use coffee machines with this conventional device.
Moreover, the helicoidal ramps are masked from the view of the operator, which is also the case of the sprinkling grill, of the compactor and above all of the cup joint, which, located at the bottom of the annular space delimited by the recess and the compressor, can be only very difficulty inspected, cleaned and replaced.
As a result, these devices, given their difficulty of access, are not easy to clean and do not satisfy the rules and regulations of construction to ensure cleanliness and use of materials suitable for foods (French Unified Standard 60.010 and USA Standard NSF (National Sanitation Foundation) Standard 4, particularly).
Moreover, this type of construction requires the provision of members of rather complicated shape, difficult to produce and as a result very costly.
There is already known from Swiss patent CH-A-162,960, a device partially overcoming certain of these drawbacks mentioned above. The recess comprises two diametrically opposed notches, opening outwardly; each notch providing two helicoidal ramps that are opposite and symmetrical. The projections for securing the filter-carrying cup are replaced by carrying rollers. Thus, the difficulties of engagement are in large part overcome, because the entry of the notches of the recess and the carrier rollers of the filter-carrying cup remain permanently visible from the exterior, and as a result, by the operator. Add to that that the filter-carrying cup can be if desired locked against the cup joint toward the left or toward the right.
However, the difficulties of cleaning remain, because the pressurizer, and above all the cup joint, remain masked from view and difficult of access.